Application strategies of saline water and nitrogen doses in mini watermelon cultivation

Salt stress is highlighted as one of the limiting factors for the establishment of agriculture in the semiarid region of Northeastern Brazil. In this context, it is essential to look for new strategies aiming at minimizing the effects of salt stress on the crops. The present work aimed to evaluate the photochemical efficiency, photosynthetic pigments, and growth of the watermelon cv. Sugar Baby under different use strategies with saline waters and nitrogen fertilization. The experiment was conducted in a protected environment at the Center of Technology and Natural Resources of the Federal University of Campina Grande, municipality of Campina Grande, Paraíba. An experimental design in randomized blocks was adopted, arranged in a 6 x 2 factorial scheme, with six management strategies of water salinity and two nitrogen doses (corresponding to 50 and 100% of the recommendation), with five replications. Two salinity levels of the irrigation water were studied, one with low and another with a high level of electrical conductivity of the water (ECw = 0.8 and 3.2 dS m-1). The watermelon cv. Sugar Baby expressed higher sensitivity to salt stress in the flowering phase, with a decrease in the synthesis of chlorophyll b, chlorophyll total, and carotenoids. The 50% dose of N provided an increment in the initial fluorescence, stem diameter, and the number of leaves of the watermelon cv. Sugar Baby. The length of the main branch of the watermelon plants decreased with the salt stress applied in the fructification phase; however, the fertilization with 100% of N stimulated a higher growth when the irrigation with saline waters was performed at the vegetative and flowering phases.Salt stress is highlighted as one of the limiting factors for the establishment of agriculture in the semiarid region of Northeastern Brazil. In this context, it is essential to look for new strategies aiming at minimizing the effects of salt stress on the crops. The present work aimed to evaluate the photochemical efficiency, photosynthetic pigments, and growth of the watermelon cv. Sugar Baby under different use strategies with saline waters and nitrogen fertilization. The experiment was conducted in a protected environment at the Center of Technology and Natural Resources of the Federal University of Campina Grande, municipality of Campina Grande, Paraíba. An experimental design in randomized blocks was adopted, arranged in a 6 x 2 factorial scheme, with six management strategies of water salinity and two nitrogen doses (corresponding to 50 and 100% of the recommendation), with five replications. Two salinity levels of the irrigation water were studied, one with low and another with a high level of electrical conductivity of the water (ECw = 0.8 and 3.2 dS m-1). The watermelon cv. Sugar Baby expressed higher sensitivity to salt stress in the flowering phase, with a decrease in the synthesis of chlorophyll b, chlorophyll total, and carotenoids. The 50% dose of N provided an increment in the initial fluorescence, stem diameter, and the number of leaves of the watermelon cv. Sugar Baby. The length of the main branch of the watermelon plants decreased with the salt stress applied in the fructification phase; however, the fertilization with 100% of N stimulated a higher growth when the irrigation with saline waters was performed at the vegetative and flowering phases

Phytomass and quality of yellow passion fruit seedlings under salt stress and silicon fertilization

The semiarid region of Northeastern Brazil is characterized by long drought periods, and the use of saline waters appears as an alternative for the expansion of irrigated areas. Associated with the use of these waters, silicon fertilization constitutes an important attenuator of salt stress. In this perspective, this study aimed to evaluate the phytomass production and quality of the passion fruit cultivar ‘Gigante Amarelo’ grown with saline water and silicon fertilization. The experiment was conducted in a plant nursery belonging to the Center of Agrifood Science and Technology, in the municipality of Pombal-PB. A completely randomized block design in a 5 x 5 factorial scheme was used, referring to five levels of electrical conductivity of the irrigation water (0.3, 1.0, 1.7, 2.4, and 3.1 dS m-1) and five doses of silicon fertilization (0; 25; 50; 75, and 100 g of potassium silicate/plant), with four replications and two plants per plot. The phytomass accumulation (leaves, stem, and roots), as well as the total dry phytomass, shoot dry phytomass, root/shoot ratio, and the quality index of Dickson were evaluated. The data obtained were subjected to the F-test at 0.01 and 0.05 level of probability. The electrical conductivity of water from 0.3 dS m-1 caused the decrease of phytomass production in seedlings of the passion fruit cultivar ‘Gigante Amarelo’, although it is possible to produce good quality passion fruit seedlings with water salinity up to 3.1 dS m-1. The doses of silicon fertilization mitigated the effect of salt stress on the root/shoot ratio of plants of the passion fruit cultivar ‘Gigante Amarelo’.The semiarid region of Northeastern Brazil is characterized by long drought periods, and the use of saline waters appears as an alternative for the expansion of irrigated areas. Associated with the use of these waters, silicon fertilization constitutes an important attenuator of salt stress. In this perspective, this study aimed to evaluate the phytomass production and quality of the passion fruit cultivar ‘Gigante Amarelo’ grown with saline water and silicon fertilization. The experiment was conducted in a plant nursery belonging to the Center of Agrifood Science and Technology, in the municipality of Pombal-PB. A completely randomized block design in a 5 x 5 factorial scheme was used, referring to five levels of electrical conductivity of the irrigation water (0.3, 1.0, 1.7, 2.4, and 3.1 dS m-1) and five doses of silicon fertilization (0; 25; 50; 75, and 100 g of potassium silicate/plant), with four replications and two plants per plot. The phytomass accumulation (leaves, stem, and roots), as well as the total dry phytomass, shoot dry phytomass, root/shoot ratio, and the quality index of Dickson were evaluated. The data obtained were subjected to the F-test at 0.01 and 0.05 level of probability. The electrical conductivity of water from 0.3 dS m-1 caused the decrease of phytomass production in seedlings of the passion fruit cultivar ‘Gigante Amarelo’, although it is possible to produce good quality passion fruit seedlings with water salinity up to 3.1 dS m-1. The doses of silicon fertilization mitigated the effect of salt stress on the root/shoot ratio of plants of the passion fruit cultivar ‘Gigante Amarelo’

Alocação de fitomassa pela mamoneira sob estresse salino e doses de nitrogênio

A escassez de água de boa qualidade é um fator limitante para a agricultura irrigada, principalmente nas regiões áridas e semiáridas e em consequência, a utilização de águas salinas na irrigação das culturas surge como alternativa. Neste sentido, objetivou-se com esta pesquisa, avaliar os efeitos da irrigação com águas salinas e da aplicação de distintas doses de nitrogênio sobre o acúmulo de biomassa da mamoneira cv. BRS Energia, em experimento conduzido em lisímetros sob condições de campo no CCTA/UFCG. Adotou-se o delineamento em blocos inteiramente casualizados em esquema fatorial 5 x 4, testando 5 níveis de salinidade da água de irrigação - CEa (0,3; 1,2; 2,1; 3,0 e 3,9 dS m-1) e 4 doses de adubação nitrogenada (70, 100, 130 e 160% da dose indicada para ensaio em lisímetro) com três repetições. A irrigação com água de CEa até 3,9 dS m-1 não exercem influência negativa sobre a alocação de fitomassa foliar e a razão de fitomassa radicular; A mamoneira cv BRS Energia altera sua alocação de fitomassa em função dos níveis salinos da água, apresentando diminuição na AFC e AFR; A razão de fitomassa caulinar e radicular decresce em função da aplicação de níveis de CEa; Não houve interação entre os fatores níveis de salinidades da água versus doses de adubação nitrogenada sobre as variáveis da mamoneira cv. BRS Energia avaliadas

Physiological indices and phytomass partition in precocious dwarf cashew clones irrigated with saline waters

This research aimed to evaluate the physiological indices and the accumulation of phytomass in clones of precocious dwarf cashew under salt stress during rootstock formation. The experiment was conducted in greenhouse in the municipality of Pombal-PB. The experimental design was in randomized blocks, and the treatments were organized in a 5 x 3 factorial arrangement, constituting the levels of electrical conductivity of the irrigation water - ECw (0.4 -Control; 1.2; 2.0; 2.8, and 3.6 dS m-1) and the clones of precocious dwarf cashew (Faga 11, Embrapa 51, CCP 76), with three replications and two plants per plot. Water salinity higher than 0.4 dS m-1 resulted in a decrease of the relative growth in plant height, leaf area, and phytomass accumulation in the cashew plant. The cashew clones are sensitive to water salinity from 0.4 dS m-1. Among the physiological indicators, the leaf area ratio, the sclerophylly index, and the root/shoot ratio of the precocious dwarf cashew are highlighted as salt stress indicators. The use of water with 0.4 dS m-1 of electrical conductivity is recommended for the formation of cashew rootstocks.This research aimed to evaluate the physiological indices and the accumulation of phytomass in clones of precocious dwarf cashew under salt stress during rootstock formation. The experiment was conducted in greenhouse in the municipality of Pombal-PB. The experimental design was in randomized blocks, and the treatments were organized in a 5 x 3 factorial arrangement, constituting the levels of electrical conductivity of the irrigation water - ECw (0.4 -Control; 1.2; 2.0; 2.8, and 3.6 dS m-1) and the clones of precocious dwarf cashew (Faga 11, Embrapa 51, CCP 76), with three replications and two plants per plot. Water salinity higher than 0.4 dS m-1 resulted in a decrease of the relative growth in plant height, leaf area, and phytomass accumulation in the cashew plant. The cashew clones are sensitive to water salinity from 0.4 dS m-1. Among the physiological indicators, the leaf area ratio, the sclerophylly index, and the root/shoot ratio of the precocious dwarf cashew are highlighted as salt stress indicators. The use of water with 0.4 dS m-1 of electrical conductivity is recommended for the formation of cashew rootstocks

Nitrate and ammonium proportions in sesame cultivation under irrigation with saline waters

This research was conducted with the aim of evaluating the water relations, growth and the production components of the sesame cv. CNPA G3, in function of the irrigation with waters of different salinities and fertilization with different proportions of nitrate (N-NO3-) and ammonium (N-NH4+). The study was performed in drainage lysimeters in conditions of greenhouse, in the municipality of Campina Grande, PB, Brazil. The adopted design was in randomized blocks, in a factorial scheme of 5x5 with three repetitions, whose treatments were constituted of five levels of electrical conductivity of the irrigation water - ECw (0.6; 1.2; 1.8; 2.4 and 3.0 dS m-1) and five proportions of nitrate and ammonium (200:0; 150:50; 100:100; 50:150; 0:200 mg kg-1 of soil). The irrigation with ECw superior to 0.6 dS m-1 negatively affected the growth and production of the sesame; the fertilization with N-NH4+ and N-NO3- in the proportion 200:0 resulted in a higher percentage of cell membrane damage; the utilization of N-NH4+ and N-NO3- in the proportion 50:150 provided increase in the relative water content in the leaf blade and in the mass of a hundred seeds; N-NO3 and N-NH4+ proportions of 200:0 and 150:50 and water with ECw of 0.6 dS m-1 promoted the highest values for the content of chlorophyll a and total number of sesame seeds.This research was conducted with the aim of evaluating the water relations, growth and the production components of the sesame cv. CNPA G3, in function of the irrigation with waters of different salinities and fertilization with different proportions of nitrate (N-NO3-) and ammonium (N-NH4+). The study was performed in drainage lysimeters in conditions of greenhouse, in the municipality of Campina Grande, PB, Brazil. The adopted design was in randomized blocks, in a factorial scheme of 5x5 with three repetitions, whose treatments were constituted of five levels of electrical conductivity of the irrigation water - ECw (0.6; 1.2; 1.8; 2.4 and 3.0 dS m-1) and five proportions of nitrate and ammonium (200:0; 150:50; 100:100; 50:150; 0:200 mg kg-1 of soil). The irrigation with ECw superior to 0.6 dS m-1 negatively affected the growth and production of the sesame; the fertilization with N-NH4+ and N-NO3- in the proportion 200:0 resulted in a higher percentage of cell membrane damage; the utilization of N-NH4+ and N-NO3- in the proportion 50:150 provided increase in the relative water content in the leaf blade and in the mass of a hundred seeds; N-NO3 and N-NH4+ proportions of 200:0 and 150:50 and water with ECw of 0.6 dS m-1 promoted the highest values for the content of chlorophyll a and total number of sesame seeds

Morphophysiology of the passion fruit ‘BRS Rubi do Cerrado’ irrigated with saline waters and nitrogen fertilization

This study aimed to evaluate the gas exchanges and growth of the purple passion fruit cultivar ‘BRS Rubi do Cerrado’ as a function of the salinity levels of the irrigation water and nitrogen fertilization. The research was conducted in pots adapted as drainage lysimeters, placed within a plant nursery, using a Regolithic Neosol of sandy texture, in the municipality of Pombal-PB, Brazil. A randomized block design was used, testing five levels of electrical conductivity of irrigation water (0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1) associated with four doses of nitrogen (50, 75, 100, and 125% of the recommendation). The irrigation water salinity above 0.3 dS m-1 compromised the leaf area and the relative water content of the purple passion fruit ‘BRS Rubi do Cerrado’. High doses of nitrogen enhance the deleterious effects of irrigation water salinity on stomatal conductance, transpiration, internal CO2 concentration, CO2 assimilation rate, number of leaves, stem diameter, and height of purple passion fruit plants. When waters with salinity levels of up to 1.3 dS m-1 are used, the dose of 125 mg of N kg-1 of soil is recommendation for providing increases in the CO2 assimilation rate of the purple passion fruit ‘BRS Rubi do Cerrado’ at 70 days after sowing (DAS). Water salinity increases electrolyte leakage, regardless of nitrogen doses.This study aimed to evaluate the gas exchanges and growth of the purple passion fruit cultivar ‘BRS Rubi do Cerrado’ as a function of the salinity levels of the irrigation water and nitrogen fertilization. The research was conducted in pots adapted as drainage lysimeters, placed within a plant nursery, using a Regolithic Neosol of sandy texture, in the municipality of Pombal-PB, Brazil. A randomized block design was used, testing five levels of electrical conductivity of irrigation water (0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1) associated with four doses of nitrogen (50, 75, 100, and 125% of the recommendation). The irrigation water salinity above 0.3 dS m-1 compromised the leaf area and the relative water content of the purple passion fruit ‘BRS Rubi do Cerrado’. High doses of nitrogen enhance the deleterious effects of irrigation water salinity on stomatal conductance, transpiration, internal CO2 concentration, CO2 assimilation rate, number of leaves, stem diameter, and height of purple passion fruit plants. When waters with salinity levels of up to 1.3 dS m-1 are used, the dose of 125 mg of N kg-1 of soil is recommendation for providing increases in the CO2 assimilation rate of the purple passion fruit ‘BRS Rubi do Cerrado’ at 70 days after sowing (DAS). Water salinity increases electrolyte leakage, regardless of nitrogen doses

Chloroplast pigments, water relationships, and growth of bell pepper under salt stress and nitrogen

The use of saline water sources for irrigation in semi-arid regions is a challenge for horticultural production since plants are sensitive to salt stress conditions, thus requiring techniques that allow plant acclimation, including nitrogen fertilization. From this perspective, this study aimed to evaluate the chloroplast pigments, water relationships, and growth of bell pepper plants irrigated with saline water and subjected to nitrogen fertilization. The experiment was conducted under field conditions at the Federal University of Campina Grande, Pombal - PB, where a randomized block design was adopted with a 5 x 5 factorial arrangement corresponding to five electrical conductivity levels of irrigation water (0.3, 1, 1.7, 2.4, and 3.1 dS m-1) and five nitrogen levels (50, 75, 100,125, and 150% of the dosage recommended for the crop), with three replications. The 125 and 150% N levels provided the highest relative water contents in bell pepper plants irrigated with electrical conductivity levels of up to 1.7 dS m-1. The contents of chlorophyll a, b, total chlorophyll, carotenoids, and stem diameter of bell pepper plants decreased when fertilized with 150% N and irrigated with the electrical conductivity of 3.1 dS m-1.The use of saline water sources for irrigation in semi-arid regions is a challenge for horticultural production since plants are sensitive to salt stress conditions, thus requiring techniques that allow plant acclimation, including nitrogen fertilization. From this perspective, this study aimed to evaluate the chloroplast pigments, water relationships, and growth of bell pepper plants irrigated with saline water and subjected to nitrogen fertilization. The experiment was conducted under field conditions at the Federal University of Campina Grande, Pombal - PB, where a randomized block design was adopted with a 5 x 5 factorial arrangement corresponding to five electrical conductivity levels of irrigation water (0.3, 1, 1.7, 2.4, and 3.1 dS m-1) and five nitrogen levels (50, 75, 100,125, and 150% of the dosage recommended for the crop), with three replications. The 125 and 150% N levels provided the highest relative water contents in bell pepper plants irrigated with electrical conductivity levels of up to 1.7 dS m-1. The contents of chlorophyll a, b, total chlorophyll, carotenoids, and stem diameter of bell pepper plants decreased when fertilized with 150% N and irrigated with the electrical conductivity of 3.1 dS m-1

Growth and physiological aspects of bell pepper (Capsicum annuum) under saline stress and exogenous application of proline

This study aimed to evaluate growth and physiological aspects of ‘All Big’ bell pepper, under saline stress and exogenous application of proline on the leaves. The research was conducted in pots adapted as drainage lysimeters under greenhouse conditions, using sandy-loam eutrophic Regolithic Neosol, in the municipality of Campina Grande-PB, Brazil. The experiment was set in randomized blocks, in order to test two levels of irrigation water electrical conductivity - ECw (0.6 and 3.0 dS m-1) associated with four proline concentrations (0, 10, 20 and 30 mmol L-1). Plants were grown in 10-L pots for 50 days after transplantation. This period corresponds to the transition of vegetative and reproductive stages, in which plants were evaluated for growth, gas exchanges and chlorophyll a fluorescence. The increase in irrigation water salinity reduced growth, gas exchanges and the efficiency of photosystem II in bell pepper plants. Proline concentrations from 12.8 to 16.8 mmol L-1 incremented the activity of gas exchanges, reducing the effect of saline stress on bell pepper plants. Proline concentrations under study did not influence chlorophyll a fluorescence of ‘All Big’ bell pepper plants.Key words: Saline water, gas exchanges, chlorophyll a fluorescence, proline

Oil content and yield of castor bean as affected by nitrogen fertilization and saline water irrigation

O objetivo deste trabalho foi avaliar o teor de óleo e a produção de sementes da mamoneira 'BRS Energia', submetida a doses de adubação nitrogenada e irrigação com água com diferentes índices de salinidade. O experimento foi realizado em lisímetros, em condições de campo, em delineamento de blocos ao acaso, com três repetições. Os tratamentos consistiram dos índices salinos da água de 0,4 (controle), 1,4, 2,4, 3,4 e 4,4 dS m‑1, associados a 50, 75, 100, 125 e 150% das doses de N recomendadas para ensaio. A interação entre salinidade da água de irrigação e doses de N não foi significativa para nenhuma variável estudada. A salinidade da água até 1,4 dS m‑1 propiciou teor de óleo das sementes de 47%. Doses de N acima de 64% da recomendada promoveram teor de óleo inferior a 48%. A maior produção de matéria seca da parte aérea foi obtida com 150% da dose de N recomendada. O incremento salino a partir de 0,4 dS m‑1 aumenta o tempo para emissão do racemo primário e reduz os valores dos componentes de produção, dos quais a massa de matéria seca da parte aérea e o número de frutos são os mais afetados. Condutividade elétrica da água de até 1,9 dS m‑1 e doses de N a partir de 134% da recomendada propiciam maior número de racemos.The objective of this work was to evaluate the oil content and seed yield of castor bean 'BRS Energia' subjected to doses of N fertilization and irrigation water with different levels of salinity. The experiment was carried out in lysimeters, under field conditions, using a randomized complete block design, with three replicates. Treatments consisted of the irrigation‑water salinity levels of 0.4 (control), 1.4, 2.4, 3.4 and 4.4 dS m‑1, associated to 50, 75, 100, 125 and 150% of the recommended N dose for trials. There was no significant interaction between irrigation water salinity and nitrogen levels for any of the studied variables. Water salinity of up to 1.4 dS m‑1 provided 47% of oil content in seeds. Nitrogen doses 64% above recommended promoted less than 48% of oil content. The highest shoot dry weight was obtained with 150% of the recommended N dose. Increasing water salinity from 0.4 dS m‑1 increases the interval for emission of the primary raceme and reduces the yield components, of which shoot dry weight and number of fruits are the most affected. Electrical conductivity of irrigation water up to 1.9 dS m‑1 and N levels up to 134% of the recommended dose provide a greater number of racemes